The Past of the Earth-Moon System: A Lecture | SF

Submitted by the Event Organizer

Bay Area Science Events

This event is curated by the Bay Area Science Festival as part of their year-round calendar of science events.

The festival takes place each fall with 10 days of science and technology lectures, games, exhibits, workshops and hands-on activities all over the Bay Area. 

> Find tons more Bay Area science events at bayareascience.org

Tuesday, October 20, 2015
Bay Area Science Events

The present Earth-Moon system formed in the aftermath of the impact of a Mars-sized body on the planet. The Earth was then mostly melted and the Moon accreted from a ring of vapor and liquid orbiting the Earth. Part of the impactor’s core ended up in the Moon-forming disk around the Earth. Iron metal within the disk was partly oxidized by ferric iron and water. Metallic iron remained and this formed the Moon’s small core, and about 2% of the impactor’s core ended up within Earth’s mantle.

It is conceivable that early asteroid bombardment on the Earth was relatively benign and that planet sterilizing impact never occurred. A dense CO2 atmosphere blanketed Earth within about 10 million years of the impact, and a solar-heated greenhouse maintained 200 degrees C temperatures at the surface.

Earth did not become habitable until the CO2 subducted into the mantle. Subducted oceanic crust carried carbonates into the mantle, which partially melted beneath island arcs to form alkaline CO2-rich lavas. Groundwaters within these lavas are an attractive prebiotic environment. By the time of Earth’s earliest sedimentary record at about 3.8 billion years ago, the surface was clement, the ocean was near its current pH about 8, and the CO2 pressure in the air was comparable to the modern value. By then, life had already begun to modify the composition of the Earth’s surface, and even its mantle.

Speaker: Norman Sleep, Stanford University

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